Aortic dissection and the connection to several rare genetic conditions
September 19 is Aortic Dissection Awareness Day. Rare Disease 360, in partnership with The Marfan Foundation, spoke with James Hamilton Black III, MD, chief of Vascular Surgery at Johns Hopkins Hospital in Baltimore, about the link between aortic dissection and several rare genetic conditions. Here’s what physicians and patients need to know.
Question:
September 19 is Aortic Dissection Awareness Day. What is the importance of highlighting and recognizing this condition?
James Hamilton Black III, MD:
In terms of the condition of aortic dissection, the problem we have from the standpoint of diagnosing it early is really that it overlaps a lot of other conditions, so statistically speaking, when people come to the emergency room with chest pain or back pain, they initially are thought to have coronary disease, and that’s not a bad thought. It’s about 4,400 out of 100,000 patient visits to the emergency room are about heart attacks and things of that nature, but aortic dissections are much, much less, so identifying the condition early, given its big overlap with other cardiovascular conditions, is always a challenge.
Question:
Patients with rare conditions like Marfan syndrome, Loeys-Dietz syndrome, and Vascular Ehlers-Danlos syndrome have a roughly 250 times greater risk of aortic dissection. What should physicians and individuals know about these conditions and the potential link to aortic dissection?
James Hamilton Black III, MD:
Broadly speaking, when you think about aortic dissections, particularly when they happen in the young, you really have to think early and often about an associated genetic component. There are some types of aortic dissections, particularly what we call a type B aortic dissection, which is more strongly associated with long-standing hypertension, and of course then you have the patient groups who have those be much, much older, but particularly an aortic dissection in the young, under 40, and definitely under 30, is almost certainly going to have a strong genetic component.
Question:
You are an expert in treating patients with aortic aneurysms. What are your surgical techniques and non-surgical recommendations?
James Hamilton Black III, MD:
The vast majority of people we see with aortic aneurysms and aortic dissections, and they are related conditions in the sense that, at least initially, most aortic dissections will start and close to normal diameter aortic segments. The one exception to that, of course, is in the aortic root where there’s a strong association with aortic dissection with enlargement of the root, which is why we try and identify those patients early, monitor them closely, and then of course they move on to heart surgery when they need it.
But the importance of surveillance really can’t be understated. Along the way, while we’re watching these either chronic aortic dissections that have some element of dilation turning to aneurysm, or we’re just following aortic segments that haven’t had dissections but are just enlarged, those are the times and the opportunities where patients can ask their doctors about what are the medical therapies they can do, and right now, blood pressure control is super important. We usually like beta blockade for when patients can tolerate it, but more importantly, there’s always investigations and science that’s improving, so sometimes going to the doc just to check up on your aorta and do the surveillance is also an opportunity to engage the question about what’s the new science coming down the road that could help someone perhaps avert needing a surgery in the future, because that science and those opportunities for treatment become available to them.
Question:
What are some ongoing research needs in this area to offer the best outcomes and care for patients with aortic dissection or any of the previously mentioned conditions?
James Hamilton Black III, MD:
There’s always research ongoing, particularly here at Hopkins with my collaborators in genetic medicine, such as Hal Dietz, Jen Pardo, and others, and in that scenario we’re really looking at what’s happening at this cellular event inside the aorta, what’s changing, what’s for the good, what’s for the bad, and trying to tilt those one way or another.
The surgical techniques for handling patients who have aortic aneurysms, particularly an aortic root, include the refinement of surgery to try and spare the aortic valve, what’s called valve-sparing root replacement, and that’s performed expertly by the cardiac surgery team here at Hopkins.
When patients have other forms of chronic dissections or type B dissections, vascular surgeons have been increasingly involved in those cases, particularly when there’s an opportunity to consider endovascular therapy. Endovascular therapy is more minimally invasive techniques to address aortic aneurysms. Those techniques are very, very dependent upon the anatomy, that is, the stents themselves have a limited number of sizes, so therefore the aorta has to match up with the devices, and that’s a very long conversation that occurs between vascular surgeons and their patients with aortic dissections and aortic aneurysms, but I think there’s good research emerging that there will be a role for stent graft therapy in many patients with aortic dissections, aortic aneurysms in various specific instances, even for patients who are perhaps younger with connective tissue disorders such as Marfan, Loeys-Dietz, and Ehlers-Danlos.
Question:
As an expert in vascular surgery and endovascular therapies, where do you see the field going for patients with Marfan syndrome, Loeys-Dietz syndrome, and Vascular Ehlers-Danlos syndrome?
James Hamilton Black III, MD:
There’s been a general belief that particularly in instances of an emergency, for example, rupture of the aorta, where even a surgical exposure could be so hazardous that it would give a surgeon or an interventionist significant hesitation, so in situations of aortic rupture, everyone would agree that a stent graft to handle a rupture of the descending thoracic aorta is the way to go.
The concern that has come up over the years, and it’s a valid one, is that the devices themselves are relatively stiff. They don’t like to take turns, and of course the vessels, when people have an underlying genetic condition, often are not straight. They have a lot of tortuosity, and that puts a lot of engineering stress on those devices.
Studies are starting to come out identifying that perhaps if the device is sitting inside a surgical graft that has been placed before, that that could provide what we call a stable landing zone, that is the stents have to land on a piece of aorta that it’s going to hold steady on, and it’s going to have to land beyond the aneurysm on another piece of aorta that has to hold steady on, and we call those the proximal landing zone and the distal landing zone more downstream, and the research is suggesting that surgical grafts are adequate to hold the devices in place, and then at that point, the next question becomes, the vessels that branch off of the aorta, are they also suitable for stent graft therapy, and that’s a very, very detailed discussion that occurs with their patients and their surgeons about those particular branches.
Frankly, what it sometimes boils down to is that the branches of the vessels are just too big and you can’t rely upon the branches coming off of the main aortic stents to then hold in place and be steady, and of course, that’s then puts the patient back in the field of what we call open surgery. Open surgery is very safe, but of course with these incisions and anesthetics and the length of the operation, it’s always a longer recovery.
